1. Field of the Invention
The present invention relates to an image pickup apparatus provided with a linear actuator for driving one or more lens groups of an optical system constituted of a plurality of lens groups in a direction along an optical axis.
2. Description of Related Art
Conventionally, image pickup apparatuses such as digital cameras or video cameras have been generally put into practical use and widely spread, and such image pickup apparatuses are configured to sequentially perform photoelectric conversion on optical images formed by an image pickup optical system by using an image pickup device such as a photoelectric conversion device, to store obtained image signals as image data in a predetermined format (for example, digital image data representing still images or moving images) in a storage medium, and configured to be able to display the still images or moving images based on the digital image data by using an image display apparatus.
The image pickup apparatus configured as described above generally includes a lens barrel composed of various constituent members including, for example, a plurality of optical lens groups which constitute an image pickup optical system, a plurality of lens holding frames that respectively hold the plurality of optical lens groups, and a lens driving unit constituted of an actuator or the like for moving one or more lens holding frames among the plurality of lens holding frames in a predetermined direction by a predetermined amount at a predetermined timing.
The types of the image pickup apparatus include, for example, various types such as what is called a lens-integrated type in which a lens barrel is configured to be integrated with a main body portion of the image pickup apparatus, a lens-changeable type in which a lens barrel is configured to be attachable to and detachable from the main body portion of the image pickup apparatus, or the like.
The lens barrel in such types of conventional image pickup apparatus includes a lens driving unit that causes one or more lens groups among a plurality of optical lens groups constituting an image pickup optical system, for example, a focus lens group for performing focus adjusting action to move in a predetermined direction along the optical axis by a predetermined amount at a predetermined timing. An example of the actuator included in the lens driving unit is the one using a linear actuator such as a voice coil motor (VCM).
For example, the image pickup apparatus disclosed in Japanese Patent Application Laid-Open Publication No. 2013-222116, which is provided with a linear actuator for driving an image pickup optical system, includes: a lens holding frame; driving magnets extended in parallel to the optical axis and configured such that the magnetic poles are alternately reversed; driving coils mounted to the lens holding frame so as to be opposed to the driving magnets, and two magnetic sensors that detect the magnetism of the driving magnets and detect the position of (the driving coils mounted to) the lens holding frame, and the linear actuator obtains a driving power for moving the lens holding frame in a direction along the optical axis by controlling the currents to be applied to the driving coils, based on signals from the two magnetic sensors.